The present invention relates to a method and system for controlling the thrust of a watercraft during various steering conditions, and more particularly to a method and system for controlling the thrust of a watercraft of the jet propulsion type.
One type of watercraft is the jet-propelled type that is designed to be operated by a rider seated on the watercraft in a straddle-like fashion. This type of watercraft is propelled by discharging water out of a discharge nozzle located at the rear of the watercraft.
To provide steering for the watercraft, a steering nozzle is pivotably connected to the end of the discharge nozzle. The input for the pivot of the steering nozzle is provided by a steering handle pivotably mounted on the top of the watercraft. To steer the watercraft to the right, the rider turns the steering handle clockwise causing the steering nozzle to pivot counter-clockwise. The discharge of water out of the steering nozzle with the nozzle pivoted counter-clockwise causes the watercraft to yaw clockwise and turn to the right. A similar but opposite sequence is used to steer the watercraft to the left. Therefore, for a watercraft of the jet propulsion type to steer properly, a sufficient amount of thrust out of the steering nozzle is required.
The thrust of the watercraft is controlled by the rider through the use of a finger operated throttle lever pivotably mounted on the steering handle. The throttle lever is biased toward an idle position. To increase thrust of water out of the discharge nozzle, the rider Cry presses down on the throttle lever with his finger. This pivots the throttle lever toward the wide-open throttle position. To decrease thrust of water out of the discharge nozzle, the rider releases the throttle lever. Since the throttle lever is biased toward the idle position, without a force countering the bias, the throttle lever pivots toward the idle position. As the throttle lever pivots toward the idle position, the thrust of water out of the discharge decreases.
While the decrease in thrust of water out of the discharge nozzle is desirable for slowing down the watercraft, the decrease in thrust of water out of the discharge nozzle also decreases the steering capability of the watercraft since the thrust provides the steering for the watercraft.
This quick decrease in steering capability is particularly problematic in situations in which an inexperienced rider attempts to avoid an obstacle directly in front of the watercraft. To properly avoid the obstacle, the rider should apply a constant pressure on the throttle lever while simultaneously turning the steering handle. However, an inexperienced rider may release the throttle lever to slow the watercraft quickly while simultaneously turning the steering handle in an attempt to maneuver around the obstacle. In such a situation, the rider may not be able to maneuver around the obstacle since steering capability has been decreased.
This decrease in steering capability is also problematic for the rider to maneuver the watercraft for docking the watercraft. Since the docking procedure usually occurs with the watercraft traveling at a low speed, the rider may release the throttle lever while attempting to dock the watercraft. However, with only idle thrust provided to steer the watercraft, steering capability may not be adequate to dock the watercraft.
The present invention is directed toward a system for controlling thrust of a jet propulsion type watercraft during various steering conditions. The system comprises a thrust mechanism for providing jet propulsion thrust, a steering mechanism for directing the jet propulsion thrust to steer the watercraft, a steering position sensor for sensing the steering position of the steering mechanism of the watercraft and a controller for determining the desired jet propulsion thrust based on the steering position of the steering mechanism received from the steering position sensor. The controller causes the thrust mechanism to increase thrust to a steerable thrust or inhibits the thrust from decreasing below a steerable thrust, if the steering mechanism is or has been rotated greater than a predetermined angle.